Particularly when the objective is a compact design and a high energy density of an electric drive associated therewith, liquid cooling is generally used to cool dynamoelectric machines. A typical area of application, in which the compact design of an electric drive plays a particularly large role, is electromobility. Due to the limited installation space in the motor vehicle, the objective is a particularly high power density of the traction machine used for the drive.
An electric machine which includes a liquid cooling system is thus known from DE102008014386A1, which has the features according to the definition of the species in Patent claim 1. To cool the stator, a cooling jacket is mounted on its outer circumference. A housing for accommodating the stator, including the mounted cooling jacket, is situated at a radial distance from the coolant. A cavity, through which a cooling medium may flow in the circumferential direction, is situated between the housing and the cooling jacket.
In the cooling system known from DE102008014386A1, it is proposed to separate an inlet hole for the cooling medium from an outlet hole with the aid of a detent plate, for the purpose of transporting a flow of cooling fluid 360 degrees around a circumference of the cavity.
The cooling jacket is generally connected to the stator in the form of an interference fit. This ensures a good heat transfer from the stator laminated core to the cooling jacket. The interference fit furthermore ensures the transmission of the torque to the load-bearing elements.
In known dynamoelectric machines, the cooling jacket and the housing are generally not manufactured from the same material. Likewise, different thermal expansion coefficients also result for these two components. As a result, the stator provided with the cooling jacket may form an interference fit together with the housing at room temperature, but this interference fit transitions to a clearance fit as the temperature rises during operation of the electric machine.